Method and apparatus for adjustment of modulation course patterns in a navigational system

Abstract

A method and apparatus for adjusting the modulation signal levels of overlapping beams which define along points of equal signal levels within the overlap a directional axis which in turn defines a desired navigation course for an airplane or similar maneuverable apparatus. At points offset from the directional axis, one or the other of the modulation signals will be greater in magnitude, depending on the direction of offset. The included angle between the two locus of points representing a predetermined difference in magnitude between the two modulating signals over the region between the landing field and the farthest reach of the beams defines the modulation course width for that particular difference in magnitude. In the illustrated embodiments, such a modulation course width may be effectively increased or decreased for a given antenna configuration and a given directional axis by altering the magnitudes of the modulation signals such that the difference in modulation levels is decreased or increased throughout the area of beam overlap. This is accomplished by introducing a portion of the modulation signal from one beam forming circuit into the other beam forming circuit, and viceversa, such that each radiated beam includes components of both modulation signals.

What is claimed is: 
     
       1. A method for adjustment of modulation course width in a guidance system for a maneuverable apparatus, comprising the steps of: generating first and second modulation signals having respectively different frequencies;   separating each of said first and second modulation signals into a first portion and a remainder portion;   combining said first portion of said first modulation signal with said remainder portion of said second modulation signal, and combining said first portion of said second modulation signal with said remainder portion of said first modulation signal, thereby forming first and second composite modulation signals;   generating a carrier signal;   modulating said carrier signal with said first composite modulation signal to produce a first modulated carrier signal and modulating said carrier signal with said second composite modulation signal to produce a second modulated carrier signal; and,   transmitting said first and second modulated carrier signals into space such that they overlap one another, thereby defining a guidance path for maneuverable apparatus along a directional axis in space in which the summed signal levels of said portions of said first modulation signal equals the summed signal levels of said portions of said second modulation signal on said modulated carrier signals, and defining a course width for said maneuverable apparatus in which the difference between said summed signal levels of said portions of said first modulation signal and said summed signal levels of said portions of said second modulation signal on said modulated carrier signals is no greater than a predetermined magnitude.   
     
     
       2. The method of claim 1, wherein said first portions of said first and second modulation signals have substantially identical signal levels and wherein said remainder portions of said first and second modulation signals have substantially identical signal levels. 
     
     
       3. A method of claim 2, wherein the signal levels of said first portions of first and second modulation signals are substantially below the signal levels of the remainder portions of the first and second modulation signals. 
     
     
       4. The method of claim 3, wherein the frequencies of said first and second modulation signls, respectively, are 90 Hz and 150 Hz. 
     
     
       5. The method of claim 1, wherein said first portions of said first and second modulation signals are in phase with the respective remainder portions thereof. 
     
     
       6. The method of claim 1, wherein said first portions of said first and second modulation signals are substantially 180° out of phase with the respective remainder portions thereof. 
     
     
       7. The method of claim 6, wherein said first portion of said first modulation signal is also summed with the remainder portion of said first modulation signal and said first portion of said second modulation signal is also summed with said remainder portion of said second modulation signal. 
     
     
       8. The method of claim 7, wherein said first portions of said first and second modulation signals have substantially identical signal levels and said reminder portions of said first and second modulation signals have substantially identical signal levels.